Use `$casts` instead of `$dates` property

[jasonmccreary]

Synopsis:

The Model $dates property was deprecated in Laravel 8. In order to keep an eye to the future, Blueprint should register any dates as $casts instead - ideally with an inferred date type.

Proposed Syntax:

models:
  Post:
    published_at: datetime nullable
    reviewed_on: date nullable

Expected Behavior:

class Post extends Model
{
    protected $casts = [
        'published_at' => 'datetime',
        'reviewed_on' => 'date',
        // ...
    ];
}